Dual mode correction of image distortion in a xerographic printing apparatus

A printing machine of the type in which a raster output scanner produces an imaging beam which scans across a movable photoconductive member at selected positions to generate latent images on the movable photoconductive member, including:

• encoding means for electrically encoding mechanical vibrations in and between the photoconductive member and the raster output scanner, and the velocity of the photoconductive member;
• separating means for separating said encoded signals into low frequency signals and high frequency signals;
• first adjusting means, responsive to said low frequency signals, for adjusting the velocity of the moving photoconductive member relative to the beam position;
• and
• second adjusting means, responsive to said high frequency signals, for adjusting the position of the beam relative to the photoconductive member movement direction.

A method of correcting image distortion in a reproduction machine due to vibrational and speed distortions in or between a moving photoconductive member and an electro-optical imaging device optically line scanning the photoconductive member as the photoconductive member moves past the imaging device, comprising the steps of:

• encoding, in electrical signals, the speed of the photoconductive member and also the relative vibrational motion between the photoconductive member and the imaging device;
• feeding said electrical signals to a signal separator;
• separating said electrical signals into lower frequency signals and higher frequency signals with said signal separator;
• feeding said lower frequency signals to control the speed of the photoconductive member;
• feeding said higher frequency signals to electrically adjust the position that said imaging device optically line scans the photoconductive member.